1. Field of the Invention
The present invention generally relates to a bead dispenser and, more particularly, to a bead dispenser system adapted for dispensing beads in an automated immunoassay analyzer.
2. Background Description
An immunoassay is a well known laboratory method used to determine the amount of an analyte in a sample such as plasma or urine. It is based on the interaction of antibodies with antigens, and because of the degree of selectivity for the analyte (either antigen or antibody), an immunoassay can be used to quantitatively determine very low concentration of drugs, hormones, polypeptides, or other analyte compounds found in a test sample. For many years, immunoassays were performed by hand by trained laboratory technicians.
Recently, many companies have begun producing automated immunoassay analyzers. Automating the immunoassay procedures can be onerous because of the large number of steps needed to be executed. For example, in a conventional scheme, a sample is mixed with a reagent and a solid support having a bound antigen or antibody. The sample is incubated such that the corresponding antigen or antibody in the sample and a labeled antigen or antibody provided in the reagent can be bound to the antigen or antibody on the solid support. The solid support is then thoroughly washed and the label (fluorescent, radioactive, chemiluminescent, or the like) is detected by an appropriate mechanism. Finally, the analyte of interest (antigen or antibody) is quantified from the detected label.
Most of today's automated immunoassay analyzers are designed for “walk away” operation, where the technician loads sample containing tubes onto a carousel and presses a start button. Thereafter, the automated immunoassay analyzer mixes appropriate reagents (often stored aboard the analyzer) with the sample, performs incubating and washing operations, detects the label, and computes the quantity of analyte in the sample from the detected label and stored calibration curves. The entire operation is typically done under computer control, and is some automated immunoassay analyzers, bar coding is used to identify the sample under test. The results of the immunoassays are typically output onto computer paper for inspection by the technician, or monitored and displayed in real time as described in U.S. Pat. No. 5,316,726.
One conventional method for introducing a solid support bearing the appropriate antibody or antigen for the desired test on the analyte is by dropping a solid support in bead form into a test tube, and then the sample and reagents are added and the desired analysis conducted. For example, a trade brochure published by Olympus (Biomedical Products Division), Wendenstrasse 14-16, 2 Hamburg 1, Germany, describes a bead storage unit comprising a plurality of bead packs mounted on a carousel. Each bead pack stores a plurality of solid support beads as a column on a spiral track, where the beads exit the bottom of the spiral track into an open-air holding receptacle adjoining the outside of the base of the bead pack. The dispensed beads are picked up by a vacuum-operated bead transport for feeding into a U-shaped reaction tube.
Another conventional bead pack is marketed by Roche Laboratories. The Roche Laboratories bead pack includes a spiral track for storing solid support beads with support beads dispensed at a centrally-located exit hole. A three-pronged mechanical pick-up device is used to grasp and transport the dispensed bead to a reaction tube.
Abbott Laboratories also manufacturers a bead dispenser device. In this device, a manual operated dispenser with a plunger housed in a chamber in a non-hermetic manner is provided. The chamber has a lower exit opening that is horizontally misaligned relative to an upper feed hole into the chamber. The plunger has a receptacle hole for receiving a bead that is aligned with the upper feed hole in the normal non-actuated position of the plunger. Manual actuation of the plunger displaces the plunger horizontally within the chamber such that a bead carried in the plunger receptacle hole is carried to and over the lower exit opening in the chamber. At this stage the bead can drop out of the dispenser device.
Still other bead dispensing devices are disclosed in several U.S. Patents. However, the bead dispensing devices disclosed in the several patents all have the shortcoming that beads may block or bridge the bead discharging opening, and that there does not appear to be any mechanism for clearing the pathway in front of the bead discharging opening.
For example, U.S. Pat. No. 2,683,554 to Mulhauser discloses a pill dispenser having a threaded neck and a central funnel portion by which tablets can be directed to an opening. At the bottom of the opening is a slide having a stop portion which prevents the pills from being discharged from the pill dispenser. The slide is spring biased in the closed position. When the slide is depressed, the stop is moved and the tablet is discharged from the opening. In Mulhauser, however, the funnel may become blocked or bridged by several tablets.
By way of further example, U.S. Pat. No. 4,101,284 to Difiglio et al. shows a dispenser mechanism having a sliding plate disposed between a reservoir and a base plate. The sliding plate, reservoir and base plate all have corresponding holes therein, and the sliding plate is biased by a spring. When the sliding plate is moved, all of the holes between the sliding plate, reservoir and base are aligned within one another so as to allow several balls to be simultaneously discharged from the dispenser. However, it appears that the beads may “jam” the mechanism of Difiglio et al., or may even block the holes of the sliding plate such that the beads cannot be properly dispensed therefrom.
Also, U.S. Pat. No. 4,230,236 to Boulter discloses a tablet dispenser having an outer case with a front section and a rear section. The front section has integrally molded upon it an upper projecting portion and a lower projecting portion which define a gate, and an inner part. The inner part is provided with a ramp and a downward sloping groove leading to a channel. The outer case is biased by a spring. In use, the inner part is depressed and the channel is aligned with the gate such that a tablet can roll into the gate. It is noted that the tablets may block the gate during use of the Boulter tablet dispenser.
Other known systems also appear to have these same shortcomings. These systems include U.S. Pat. No. 4,405,060 to Hsei, U.S. Pat. No. 4,415,098 to Hass and U.S. Pat. No. 4,937,048 to Sakai et al., for example.
There thus remains a need for a bead dispenser which is capable of ensuring that beads do not block or otherwise bridge a ball receiving channel, which would otherwise result in a possible test failure or incorrect bead distribution. There also remains a need for a bead dispenser device that can store and dispense beads in a hermetically-sealed manner.